In U.S. Pat. No. 4,880,623 R. Piergiorgio describes a solid pharmaceutical formulation in which Nifedipine is combined with polyethylene glycol (PEG) and the mixture is coprecipitated onto a micronized excipient. Alternatively, PEG may be precipitated onto a homogeneous mixture of the micronized Nifedipine and excipient. In either case the object is to exploit the surfactant properties of PEG so that upon drying the coated surfaces repel one another and protect the microparticles from the agglomerating effects which would otherwise occur.
The difficulty with surfacants however is their high molecular weight and their introduction to the system of lipophilic and hydrophilic groups. In principle these groups enhance stability by lowering interfacial tensions; however, in practice they also alter the physicochemical nature of the various interfaces and change the relationship between the active ingredient and other components of the composition.
In U.S. Pat. No. 4,938,962 M. Trebosc describes a topical formulation in which vitamin E and microparticles of a caffeine metal carboxylate are combined with an insoluble hydroalcoholic gel. The object is to provide a heterogenous cosmetic with slow-release capabilities for use as a slenderizer in treating cellulitis. The micronized particles are released from the gel slowly over a period of time and the insolubility of the active ingredient in the carrier ensures product efficacy.
Although Trebosc improves on topically administered formulations his procedure has no relevance to compositions in which the active ingredient is administered orally for immediate release.